Many types of manufactured goods must be packaged in containers for warehouse storage at the manufacturer's plant and for shipment by truck or rail car to a customer or to an intermediate distribution center. Often these manufactured goods are heavy and bulky, such lawn and garden tractors, outboard motors, large electrical motors, refrigerators, stoves, central air conditioners and heating units, and the like.
The container for these goods serves the functions of protecting the article from damage and providing a structure for handling and transporting the goods. The container for such large and heavy goods must have sufficient structural strength to allow the goods to be handled and to be stacked five or six containers high in a warehouse. Stacking saves warehouse space and associated freight shipping costs. For example, garden tractors typically weight up to 500 pounds each and typically are between forty-eight and sixty inches long. One manufacturer produces over 2000 tractors per day. The manufacturer must be able to place at least six of the tractors in a stack to reduce the required warehouse space for handling this large volume of production.
In the case of odd-shaped goods such as lawn tractors, outboard motors, electric motors, and the like, the goods themselves typically have no natural top or wall that allows the inherent strength of the goods to assist in stacking. The container itself therefore must possess sufficient strength in its sidewalls to allow several thousand pounds of package goods to be stacked on top of the lower-most container. It is standard procedure in the packaging industry to design such structural containers with adequate safety factors to insure that stacks of goods do not collapse due to stress in stacking and due to environmental changes such as conditions of high heat and humidity. Corrugated paperboard, for instance, may lose up to 50% of its stacking strength during conditions of high humidity when the paper liners and medium composing the corrugated board absorb atmospheric moisture. It is typical to design a container with a safety factor of 4-to-1 or 4.5-to-1 times the actual calculated load on the bottom container. For example, garden tractors weighing 325 pounds are to be stacked six high. The bottom container carries the load of five containers and tractors. The load equals 5 times 325 pounds, or a total of 1625 pounds impressed upon the lowermost container in the stack. Using a 4-to-1 safety factor, the container for these goods would need to have a top load compression strength of 6500 pounds.
In addition, containers are stacked in tractor trailers or rail cars transporting the goods. It is often desirable to stack goods two, three, or four containers high depending on the physical height of the container and the inside height of the truck trailer or rail car. Stacking saves space and reduces freight costs per container. Transit by truck or rail car however places great torque or twisting forces on the lower containers in a stack. These forces arise from road shocks, stops, starts, and cornering. The container therefore must have sufficient structural strength so as not to collapse in transit. In addition, handling of containers by forktruck or squeeze (clamp) truck exerts extreme force on the bottoms and side walls of the containers carrying heavy items. Such handling is often rough and at a fast pace. It is not uncommon for such containers to be handled many times through a distribution cycle and the container must be rugged enough to withstand this repetitive handling.
To meet the need for packaging heavy, large goods, various containers have been developed and used. These include wooden crates and corrugated packages. Wooden crates include wood-sided boxes and wire-bound wooden boxes. Wooden boxes are expensive, heavy and bulky, and are difficult to assemble on a manufacturing line. Corrugated packages include all-corrugated containers and wood reinforced corrugated containers. The all-corrugated packages include internal corrugated paperboard rollups that form corner posts for compression strength.
Wood reinforced corrugated containers however are the choice for many manufacturers of these large and heavy goods. One such container is described in U.S. Pat. No. 4,832,256 issued to Grigsby. Wood members called cleats are fixed to the sidewall of the corrugated paperboard body of the container. The cleats provide support and bracing for stacking, handling and shipment of the container as described above. The width and thickness of the wood cleats are designed to provide the desired performance characteristics of the container with the specified safety factor, as discussed above. Typically, a large container such as for a garden tractor or outboard motor would utilize one cleat fixed vertically near each corner of the container. Other vertical cleats for stacking strength are often located centrally on the other length or width panels of the body of the container. These central cleats provide additional support. A wooden base or pallet is typically provided on which the product to be packaged is fixed, either by chocking, banding, or combination. A wooden top frame often is also provided, which rests on the upper ends of the vertical wood cleats. The top frame forms a reinforced upper surface that spreads or distributes the load of other containers stacked on top. The top frame further protects the goods in the container from damage, for example, preventing a smaller package placed on top from falling through during transit.
There are many advantages of wood reinforcement cleats for corrugated containers. Wood is extremely strong on a weight basis, and is easily machinable with standard cutting, ripping and tenoning machines. Tenoning machines cut special notches or extensions which mate with a recess, called a mortise, to form a locking joint in a wood frame. Wood will not lose its strength in conditions of high heat and humidity as does corrugated paperboard. Wood however, has several major disadvantages. Increasing environmental awareness has become a factor in container design and use. Wood is difficult to readily recycle, and hence many wood packaging components are finally disposed in landfills. Available landfill sites however are becoming full and are being closed. If landfill disposal is available, fees for dumping such bulky materials are increasing. Many customers of manufacturers of the heavy durable goods described above therefore are demanding fully recyclable packaging. In response, the recycling industry has increased the number and locations of processing mills where corrugated containers are re-pulped to form new rolls of recycled liner board.
In addition, wood supplies are limited and this causes the price of wood to increase. Cutting boards for packaging wood requires harvesting of old growth, large trees, which are more importantly needed for construction lumber. Corrugated paperboard and solid fibreboard is made from pulp wood which are typically small trees rapidly grown on managed tree farms. Wood residue from sawmills and wood-using industries also can be ground up and pulped into kraft paper for solid fibre and corrugated paperboard.
Corrugated paperboard by itself, however, does not have the necessary strength to replace wood in heavy structural uses, such as the packaging requirements desired above.
Tubes of corrugated paperboard and of fibreboard have been manufactured and used as vertical cleats in containers. Typically these tubes are circular or triangular in cross-section. Corrugated paperboard is formed with relatively thin paper liners and fluted mediums, so the density of corrugated paperboard is low compared to wood in a given sized member. The associated compression and bending strength of a paperboard cleat is significantly less than with a wood member. Therefore, a large number of scored and folded forms are necessary to provide a container with sufficient top load compression strength to replace a wood cleat. The size and cost of such numerous forms typically are not competitive with wood. The goods may also have dimensional constraints that limit the placement and size of the support forms. An increased number of corrugated columns and the internal dimension constraints may require an excessively large container to hold the goods and the support forms. It is always desirable, however, to keep the outside dimensions of the container as small as possible, so that freight and storage costs can be minimized. If the product to be packaged is of such a shape as to fit relatively tightly into the corners of the container, then a large corner column cleats may not be allowed. One example of this is the wheels of a lawn tractor fitting closely into the corners of the container. The container would have to be larger to accommodate the goods and the support forms.
Accordingly, there is a need in the art for an improved structural member for use in containers for heavy goods.